I use an ORTF pair of cmc64s in the center, flanked by an AB spaced pair of Neumann km183s (pointing straight out normally, but can be directed if needed). If you google boojum/jnorman, you can find a few photos of the array setup, as well as links to several posts that discuss it.
Jim

If you like to use coincident mic techniques, you can put an MS pair in the middle of the boojum/jnorman array. Boojum recommended this to me as it permits more adjustments in post (width as well as the directional/omni blend). Faulkner does not do this with his array, as he stated that he doesn't like the sound of coincident pairs. Ultimately the combination of omni and directional mics in a single array is not the perfect solution - just a good compromise in many situations that don't permit extensive sound checking and unfettered mic placement. I'm a fan.

If you like to use coincident mic techniques, you can put an MS pair in the middle of the boojum/jnorman array. Boojum recommended this to me as it permits more adjustments in post (width as well as the directional/omni blend). Faulkner does not do this with his array, as he stated that he doesn't like the sound of coincident pairs. Ultimately the combination of omni and directional mics in a single array is not the perfect solution - just a good compromise in many situations that don't permit extensive sound checking and unfettered mic placement. I'm a fan.

One of those compromises seems to be that, if ORTF is used as the central pair, the spatial positioning of instruments across the left to right panorama is different between the central pair and the wider (67cm) omnis.

Thus, if the 2 pairs are mixed together at close to equal gain, there will be a positional 'blurring' of instruments which is unpleasant to the ear....a bit like looking through binoculars with one eyepiece out of focus.

Hence there's been a recommendation to let one pair of mics predominate over the other pair by about 7dB or more, which tends to minimise this divergent image overlay. If the central pair of directional mics are widened from ORTF out to somewhere between 41-47 cms, this image position discrepancy is similarly minimised

One of those compromises seems to be that, if ORTF is used as the central pair, the spatial positioning of instruments across the left to right panorama is different between the central pair and the wider (67cm) omnis.

Thus, if the 2 pairs are mixed together at close to equal gain, there will be a positional 'blurring' of instruments which is unpleasant to the ear....a bit like looking through binoculars with one eyepiece out of focus.

Hence there's been a recommendation to let one pair of mics predominate over the other pair by about 7dB or more, which tends to minimise this divergent image overlay. If the central pair of directional mics are widened from ORTF out to somewhere between 41-47 cams, this image position discrepancy is similarly minimised

When I first started using this setup, it was because I was working in some halls in Portland that I was not familiar with, and I was hedging my bets. It was simply to give me a choice during post to use either the ORTF pair if the space was more reverberant than I expected, or to use the omnis if the space (and mic placement) was good enough to allow it. I made a few mixes with blended pairs at various balance levels that worked well enough, but generally I found that blending seemed (to me, at least) to work best by using the ORTF pair for the main image, and using a severe LP filter (cutting everything above 200-500hz or so) on the omnis to utilize the superior low end capture that true pressure mics offer but keep the precise soundstage of the ORTF pair. Varying the LP cutoff frequency allows a certain amount of control over adding/reducing hall ambience into the overall mix.

Agree in principle, with the added caveat that it also be located in the proper place. Which in many concert recording scenarios is either impossible or compromised...due to audience seating, hall management rules, cranky video people, etc. That's why the 4 mic array is the 'default rescue job', to make the best of a bad situation, when 'proper' just isn't possible.

Once the 'coherence in image overlay issue' is sorted (via tweaking inner pair distance and angles) it's remarkable how many more hits than misses the array can pull off in practice !

Good training too, for when the compromised mic stand location is replaced by the optimal, in those better calibre gigs It's my default 3rd choice, if either an AB Omni or a directional pair don't cut it first...

my default 3rd choice, if either an AB Omni or a directional pair don't cut it first...

And in a live setting with maybe an hour to set up, often with no sound check, isn’t it just that much easier to have them all on the same stand together already? I think it’s a very fine solution to modern circumstances in much of live classical music recording these days.

And in a live setting with maybe an hour to set up, often with no sound check, isn’t it just that much easier to have them all on the same stand together already? I think it’s a very fine solution to modern circumstances in much of live classical music recording these days.

I think the answer is...it depends ! Upon your setup and sound-check/balance- check time window, and how familiar you are with the location you're working in, as well any restrictions on mic placement. Any or all of those 3 factors can sway your decision to go for a single vs double pair of main mics.

David's right, a single pair in the optimal place is going to give the best result, but the opportunity for all of the above variables to coincide favourably are typically going to vary, unless you always record in a very limited number of locations that you're very familiar with ?

On the notion of a Boojum/Norman/Faulkner array being in the wrong place for all 4 mics....my experience is that reality is rarely that unfortunate ! Typically, in a scenario where your stand placement is limited, it's still going to fall in a location where one or the other pair is close to ideal...and that's where the blend comes to the rescue.

Theory would suggest that, for the same direct:reverberant ratio, a cardioid pair should be 1.7 times the distance from the players than an Omni pair. I wonder if the upshot of that is simply the effectiveness of the array to bridge that 1-1.7 divide ? Or else, that it really shouldn't work at all ?

Ah David - and there it is. That is sort of the formulaic setup we all tend to start from, and in ideal conditions, we have the time and opportunity to adjust that to suit the sound of the hall. But very often, we have no available alternative to “well, that’s about where the mics need to go” based on audience needs, keep fire lanes open, can’t put the mic stand on the stage (or vice versa), etc, added to inadequate familiarity with the “sound” of the hall, etc, and then you’re starting to wonder, will my AB omnis be the best, or do I need a directional array like NOS cards due to being maybe a little further out than I wanted? It is just hedging your bets and giving yourself some options during post. I know that AB omnis at 12 feet out will be insanely reverberant at St Mary’s cathedral, while the same setup at the Mt Angel Abbey library auditorium will be quite dry, but when faced with an unknown venue in another city, it helps to cover your bases, yes? There is no down side that I see...

So humor me here. We have a gig where there is no sound check or time for a sound check in a totally unfamiliar hall. Low budget gig. Low budget sound expected.

A stereo main pair array between 3 to 4m from the ensemble and 3 to 4 m in the air will work. We all know that.

The availability of 3-4 metres behind the ensemble is a desirable, reasonable expectation....but any number of audience seating or hall mgt constraints can render that impossible...and that's where the 4 mic bar kicks in.

Even if 'low budget sound' is expected, why settle for such easy, low hanging fruit...when a blend of 2 pairs may have the capability of extracting more from the room than a single pair, with no necessary recourse to plug in reverb or eq or compression as you might with a textbook single pair.

If the pairs are located correctly on the bar, so that each pair is throwing a complementary stereo image to its partner, you do have the option to use some (or no ) blend, as deemed necessary. My experience is that it's never 50/50....more like 70/30, 80/20 or 90/10. If the directional pair are giving most of what's necessary, but a sense of bass extension/foundation and ambience are deficient, it's possible to use selective filtering of the Omni pair to provide that component only, as per Jim's description in post #7 ...

I'd argue it has more in common with a Decca Tree than differences from it: both are spaced, phased arrays, both probably don't augur well from a purely mathematical, theoretical standpoint...but they are empirical responses to practical situations (and they work !)

The availability of 3-4 metres behind the ensemble is a desirable, reasonable expectation....but any number of audience seating or hall mgt constraints can render that impossible...and that's where the 4 mic bar kicks in.

Even if 'low budget sound' is expected, why settle for such easy, low hanging fruit...when a blend of 2 pairs may have the capability of extracting more from the room than a single pair, with no necessary recourse to plug in reverb or eq or compression as you might with a textbook single pair.

If the pairs are located correctly on the bar, so that each pair is throwing a complementary stereo image to its partner, you do have the option to use some (or no ) blend, as deemed necessary. My experience is that it's never 50/50....more like 70/30, 80/20 or 90/10. If the directional pair are giving most of what's necessary, but a sense of bass extension/foundation and ambience are deficient, it's possible to use selective filtering of the Omni pair to provide that component only, as per Jim's description in post #7 ...

I'd argue it has more in common with a Decca Tree than differences from it: both are spaced, phased arrays, both probably don't augur well from a purely mathematical, theoretical standpoint...but they are empirical responses to practical situations (and they work !)

setting up mains isn't really someting that needs much time! if not being sure about conditions/having almost no time (or not wanting to waste any), i wouldn't set up four mics under uncertain terms though but rather go with a main pair and use two mics as spots or ambis - or use a soundfield right from the start!

in case you haven't used one, give it a try: it gives you lots of options and can save your ass (besides setup time) - i'd take one any day over (almost) any spaced array in (almost) any situation!

[btw: there's a big difference between decca (with one mic being much more into/over the orchestra) and any other spaced array! pickup of direct sound, reflections and room sound plus the possible center image also being vastly different, in addition to phase coherence as from four mics)

guess i don't need to repeat my preference for coincident systems and directional mics (as they allow to adjust a few things while mixing)...